Endovascular stents are generally used in preventing restenosis or closure by tumors of passageways and ducts in the body of a patient and for percutaneous repair of aneurysms.
From EP-A-0 480 667, a stent assembly of this kind is known in which the metal wire bodies of one or more stent segments are surrounded by a flexible, elastic sleeve, e.g. of nylon, covering the gaps between the struts of the metal wire bodies. The joints between the struts at either end of each segment are shaped into eyes by bending the wire to form a cusp and, then, welding or soldering the wire back upon itself. The stent segments are firmly attached to the flexible sleeve either by stitching, gluing or embedding the segments in the sleeve when the latter is made of a plastic material. The stent segments are connected with each other by tying the eyes formed at the joints of two segments with thread.
Whereas this prior art device is capable of percutaneous implantation, e.g. in the biliary duct, and is effective for permanent prevention of ingrowth of a tumor between the struts of the segment due to the flexible sleeve, it suffers from various practical disadvantages. On one hand, the manufacture is relatively complicated due to the welding or soldering operation required for forming the eyes at the joints of the struts and the mutual connection of stent segments by tying the eyes of two stent segments positioned end to end with thread. Since proper implantation requires the stent assembly to be able to resist contraction along the axis, application of the sleeve material to the stent segments must take place in the compressed condition of the latter.
Moreover, the thread used for tying the eyes of two segments together will add to the minimum thickness of the stent in the compressed condition which sets a lower limit to the internal diameter of the catheter used for percutaneous introduction.
From published international patent application WO 92/06734, a multistage stent assembly is known which is made up of a number of unit structures that are prevented from separation by means of rod-like connecting members joining the bends of appointed structures together. The assembly is wrapped by a mesh made, e.g., of nylon coated with silicone rubber. Also in this prior art stent, the additional connecting members will add to the minimum thickness of the stent assembly in the collapsed condition.